Communication control device, communication control method, and terminal device

ABSTRACT

There is provided a communication control device including a radio communication unit which communicates with one or more terminal devices in a cell over a channel in which a link direction is allowed to be dynamically set for each sub-frame which is a unit of time in radio communication, and a control unit which controls allocation of communication resources to the terminal device based on the setting of the link direction of the channel and a location of the terminal device in the cell.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims the benefit under 37U.S.C. §120 of U.S. patent application Ser. No. 14/397,906, titled“COMMUNICATION CONTROL DEVICE, COMMUNICATION CONTROL METHOD, ANDTERMINAL DEVICE”, filed Oct. 30, 2014, which is the national stagefiling under 35 U.S.C. §371 of international PCT Application No.PCT/JP2013/056993, filed Mar. 13, 2013, which claims priority under 35U.S.C. §119 to Japanese Patent Application No. JP2012-108874, filed inthe Japan Patent Office on May 10, 2012, the entire contents of each ofwhich is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to communication control devices,communication control methods, and terminal devices.

BACKGROUND ART

At present, radio communication systems which are compliant with LTE(Long Term Evolution), which is a standard developed by the ThirdGeneration Partnership Project (3GPP), have been introduced. Moreover,as a fourth generation standard for radio communication systems,LTE-Advanced is being studied. In radio communication systems compliantwith LTE or LTE-Advanced, frequency-division duplex (FDD) ortime-division duplex (TDD) may be employed.

In radio communication systems compliant with LTE, FDD is typicallyemployed. TDD has several advantages over FDD. For example, in FDD, itis necessary to provide a pair of an uplink frequency band and adownlink frequency band, while, in TDD, it is necessary to provide asingle frequency band. Also, in FDD, the ratio of uplink communicationresources and downlink communication resources is fixed, while, in TDD,the ratio of uplink communication resources and downlink communicationresources is variable. Specifically, in TDD, the ratio of uplinkcommunication resources and downlink communication resources can bechanged by changing the link direction configuration of each sub-framein a radio frame. Because of such advantages, it is expected that TDDwill be increasingly employed in radio communication systems compliantwith LTE or LTE-Advanced. Therefore, various techniques related to LTETDD have been proposed.

For example, Patent Literature 1 discloses a technique of shifting theboundary between a downlink sub-frame and an uplink sub-frame, andcommunicating with another Home NodeB using a sub-frame between theboundaries before and after the shifting, thereby achieving radiocommunication between Home eNodeBs.

CITATION LIST Patent Literature

Patent Literature 1: JP 2012-10310A

SUMMARY OF INVENTION Technical Problem

In TDD, the ratio of uplink communication resources and downlinkcommunication resources is variable, and therefore, different linkdirection configurations may be set for different cells, taking thedownlink or uplink traffic rate into account. However, when differentlink direction configurations are set for different cells, related cellsmay have different link directions in the same sub-frame, and as aresult, interference may occur between the related cells. For example,when a piece of user equipment (UE) which is receiving a downlink signalfrom an eNodeB in a cell receives an uplink signal of a UE in a celladjacent to that cell, the uplink signal may interfere with the downlinksignal. When the link direction configuration is dynamically set basedon an increase or decrease in the uplink or downlink traffic rate ineach cell in order to further improve throughput, it is considerablydifficult to control the interference between cells.

Therefore, it is desirable to reduce the interference between relatedcells while improving throughput in a radio communication systememploying TDD.

Solution to Problem

According to the present disclosure, there is provided a communicationcontrol device including a radio communication unit which communicateswith one or more terminal devices in a cell over a channel in which alink direction is allowed to be dynamically set for each sub-frame whichis a unit of time in radio communication, and a control unit whichcontrols allocation of communication resources to the terminal devicebased on the setting of the link direction of the channel and a locationof the terminal device in the cell.

According to the present disclosure, there is provided a communicationcontrol method including communicating with one or more terminal devicesin a cell over a channel in which a link direction is allowed to bedynamically set for each sub-frame which is a unit of time in radiocommunication, and controlling allocation of communication resources tothe terminal device based on the setting of the link direction of thechannel and a location of the terminal device in the cell.

According to the present disclosure, there is provided a terminal deviceincluding a radio communication unit which communicates with a basestation in a cell over a channel in which a link direction is allowed tobe dynamically set for each sub-frame which is a unit of time in radiocommunication. The radio communication unit communicates with the basestation according to allocation of communication resources to theterminal device itself by the base station based on the setting of thelink direction of the channel and a location of the terminal deviceitself in the cell.

Advantageous Effects of Invention

As described above, according to the present disclosure, according tothe communication control device, communication control method, andterminal device, the interference between related cells can be reducedwhile improving throughput in a radio communication system employingTDD.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram for describing an example radio frame format of TDD.

FIG. 2 is a diagram for describing an example special sub-frame includedin a radio frame of TDD.

FIG. 3 is a diagram for describing an example link directionconfiguration of each sub-frame in a radio frame of TDD.

FIG. 4 is a diagram for describing example interference in a sub-framein which a link direction is different between adjacent cells.

FIG. 5 is a diagram for describing a first example interference in asub-frame in which a link direction is different between a macrocell anda small cell.

FIG. 6 is a diagram for describing a second example interference in asub-frame in which a link direction is different between a macrocell anda small cell.

FIG. 7 is a diagram for outlining a first embodiment.

FIG. 8 is a block diagram showing an example configuration of an eNodeBaccording to the first embodiment.

FIG. 9 is a block diagram showing an example configuration of a UEaccording to the first embodiment.

FIG. 10 is a flowchart showing an example schematic flow of acommunication control process according to the first embodiment.

FIG. 11 is a diagram for outlining a variation of the first embodiment.

FIG. 12 is a diagram for describing operations of an eNodeB and a UE ina small cell.

FIG. 13 is a diagram for describing example selection of sub-frames usedin communication in a small cell.

FIG. 14 is a flowchart showing an example schematic flow of acommunication control process according to a variation of the firstembodiment.

FIG. 15 is a diagram for outlining a second embodiment.

FIG. 16 is a diagram for outlining the second embodiment.

FIG. 17 is a block diagram showing an example configuration of an eNodeBaccording to the second embodiment.

FIG. 18 is a flowchart showing an example schematic flow of acommunication control process according to the second embodiment.

FIG. 19 is a diagram for outlining a third embodiment.

FIG. 20 is a block diagram showing an example configuration of an eNodeBaccording to the third embodiment.

FIG. 21 is a flowchart showing an example schematic flow of acommunication control process according to the third embodiment.

FIG. 22 is a diagram for outlining a fourth embodiment.

FIG. 23 is a block diagram showing an example configuration of an eNodeBaccording to the fourth embodiment.

FIG. 24 is a flowchart showing an example schematic flow of acommunication control process according to the fourth embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the appended drawings. Note that,in this specification and the drawings, elements that have substantiallythe same function and structure are denoted with the same referencesigns, and repeated explanation is omitted.

Note that a description will be given in the following order.

1. Introduction

-   -   1.1. General Idea of TDD    -   1.2. Technical Problem with TDD

2. First Embodiment

-   -   2.1. Overview    -   2.2. Configuration of eNodeB    -   2.3. Configuration of UE    -   2.4. Flow of Process    -   2.5. Variations

3. Second Embodiment

-   -   3.1. Overview    -   3.2. Configuration of eNodeB    -   3.3. Flow of Process

4. Third Embodiment

-   -   4.1. Overview    -   4.2. Configuration of eNodeB    -   4.3. Flow of Process

5. Fourth Embodiment

-   -   5.1. Overview    -   5.2. Configuration of eNodeB    -   5.3. Flow of Process

6. Summary

<<1. Introduction>>

Firstly, the general idea of TDD and a technical problem with TDD willbe described. Although the general idea and technical problem, andembodiments, will be described herein using a radio communication systemcompliant with LTE or LTE-Advanced as an example, the present disclosureis, of course, not limited to the example.

<1.1. General Idea of TDD>

The general idea of TDD will be described with reference to FIGS. 1-3.

(TDD in LTE)

In LTE, any one of FDD and TDD may be employed. In FDD, anuplink-dedicated frequency band and a downlink-dedicated frequency bandare used in the frequency direction. Also, in FDD, a format in which aradio frame includes 10 sub-frames is used in the time direction. On theother hand, also in TDD, a format in which a radio frame includes 10sub-frames is used in the time direction. However, in TDD, the samefrequency band is used for both uplink and downlink communication. Theradio frame format in TDD will now be more specifically described withreference to FIG. 1.

FIG. 1 is a diagram for describing an example radio frame format of TDD.Referring to FIG. 1, the radio frame is a unit of time in LTE, which hasa length of 10 ms. Moreover, one radio frame includes 10 sub-frames. Thesub-frame is also a unit of time in LTE, which has a length of 1 ms. InTDD, the link direction is set for each sub-frame. For example, in theradio frame of FIG. 1, the link direction of the sub-frame #0 is set tothe downlink direction, and the link direction of the sub-frame #3 isset to the uplink direction.

Here, “uplink” refers to communication from a UE to an eNodeB, and“downlink” refers to communication from an eNodeB to a UE. In FIG. 1, D,U, and S indicate a downlink sub-frame, an uplink sub-frame, and aspecial sub-frame, respectively. The special sub-frame will be describedbelow.

In radio communication systems compliant with LTE, FDD is typicallyemployed. However, TDD has several advantages over FDD.

For example, TDD has an advantage in terms of provision of a frequencyband. In FDD, it is necessary to provide a pair of an uplink frequencyband and a downlink frequency band, while, in TDD, it is necessary toprovide a single frequency band.

Also, for example, TDD has an advantage in terms of the ratio of uplinkand downlink. As an example, in FDD, when an uplink frequency band of 20MHz and a downlink frequency band of 20 MHz are provided, the ratio ofuplink communication resources and downlink communication resources isfixed to “one to one.” On the other hand, in TDD, when a frequency bandof 20 MHz is provided, the ratio of uplink communication resources anddownlink communication resources is variable. Specifically, in TDD, bychanging the link direction configuration (hereinafter referred to as a“TDD configuration”) of each sub-frame in a radio frame, the ratio ofuplink communication resources and downlink communication resources canbe changed.

Because of such advantages, it is expected that TDD will be increasinglyused in radio communication systems compliant with LTE or LTE-Advanced.

Although TDD has the above advantages, it is necessary to allocate aperiod of time for switching between downlink and uplink. Therefore, inTDD, a special sub-frame is inserted between a downlink sub-frame and anuplink sub-frame. The special sub-frame will now be more specificallydescribed with reference to FIG. 2.

FIG. 2 is a diagram for describing an example of the special sub-frameincluded in the radio frame of TDD. Referring to FIG. 2, the sub-frames#0-#2 of the radio frame of FIG. 1 are shown. Here, the sub-frame #0 isa downlink sub-frame, the sub-frame #1 is a special sub-frame, and thesub-frame #2 is an uplink sub-frame. For an eNodeB, time when a UEreceives the downlink signal of the sub-frame #0 is caused to be laterthan the time of the sub-frame #0 in the format due to a transmissiondelay in space and a process delay in the UE. Also, in order to causedata to arrive at the eNodeB at the time of the sub-frame #2 in theformat, the UE needs to transmit an uplink signal in advance. Therefore,the special sub-frame is defined as a region for allocating a period oftime corresponding to the delay of downlink and a period of time bywhich uplink is advanced. Specifically, the special sub-frame includes adownlink pilot time slot (DwPTS) and an uplink pilot time slot (UpPTS).Also, the special sub-frame further includes a guard period. Thus, TDDhas the disadvantage that a special sub-frame is inserted duringswitching between downlink and uplink.

(Specific TDD Configuration)

LTE TDD is defined in 3GPP Release 8. In “TS 36.211 Table 4.2-2:Uplink-Downlink configurations,” the link direction configuration (i.e.,the TDD configuration) of each sub-frame in the radio frame of TDD isshown. The TDD configuration will now be more specifically describedwith reference to FIG. 3.

FIG. 3 is a diagram for describing an example of the link directionconfiguration of each sub-frame in the radio frame of TDD. Referring toFIG. 3, in 3GPP, seven TDD configurations, i.e., configurations 0-6, aredefined. As described above, in LTE TDD, the radio frame includes 10sub-frames, and the link direction is set for each sub-frame. In thesub-frames #0 and #5 of the 10 sub-frames, a synchronization signal istransmitted from an eNodeB, and therefore, the link directions of thesub-frames #0 and #5 are invariably fixed to the downlink direction.Moreover, the sub-frame #1 is a special sub-frame in any TDDconfiguration. Also, the link direction of the sub-frame #2 is fixedlyset to the uplink direction. On the other hand, the sub-frame #6 iseither a special sub-frame or a downlink sub-frame. The link directionsof the sub-frames #3, #4, #7, #8, and #9 are set to either the uplinkdirection or the downlink direction.

It is typically supposed that each operator selects and uses any one ofthe seven TDD configurations. Therefore, for example, it is not supposedthat each operator sets different TDD configurations for adjacent cells.

<1.2. Technical Problem with TDD>

Next, a technical problem with TDD will be described with reference toFIGS. 4-6.

(Example Specific Interference)

In the 3GPP Plenary Meetings held in Kansas City in March 2011, adecision was made to study the interference problem by setting differentTDD configurations for adjacent cells. As a result, in LTE TDD, thegeneral trend has been toward setting of different TDD configurationsfor related cells (e.g., adjacent cells). Specific interference whichoccurs when different TDD configurations are set for related cells(e.g., for adjacent cells, or for a macrocell and a small cell) will nowbe more specifically described with reference to FIGS. 4-6.

FIG. 4 is a diagram for describing example interference in a sub-framein which the link direction is different between adjacent cells.Referring to FIG. 4, a cell 10 a and a cell 10 b adjacent to the cell 10a are shown. Also, in the cell 10 a, there are an eNodeB 11 a and a UE21 a. In the cell 10 b, there are an eNodeB 11 b and a UE 21 b. Here, itis assumed that, in some sub-frame, the link direction is the downlinkdirection in the cell 10 a, while the link direction is the uplinkdirection in the cell 10 b. In this case, when the UE 21 a which isreceiving a downlink signal 13 from the eNodeB 11 a in the cell 10 areceives an uplink signal 23 from the UE 21 b in the cell 10 b, theuplink signal 23 may interfere with the downlink signal 13. Also, whenthe eNodeB 11 b which is receiving the uplink signal 23 from the UE 21 bin the cell 10 b receives the downlink signal 13 from the eNodeB 11 a inthe cell 10 a, the downlink signal 13 may interfere with the uplinksignal 23. Specifically, the interfering signals are indicated by adotted line in FIG. 4.

FIG. 5 is a diagram for describing a first example of the interferencein a sub-frame in which the link direction is different between amacrocell and a small cell. Referring to FIG. 5, a macrocell 30 and asmall cell 40 are shown. The macrocell 30 covers all or part of thesmall cell 40. Also, in the macrocell 30, there are an eNodeB 31 and aUE 21 c. In the small cell 40, there are an eNodeB 41 and a UE 21 d.Here, it is assumed that, in some sub-frame, the link direction is thedownlink direction in the macrocell 30, and the link direction is theuplink direction in the small cell 40. In this case, when the UE 21 cwhich is receiving a downlink signal 33 from the eNodeB 31 in themacrocell 30 receives an uplink signal 25 from the UE 21 d in the smallcell 40 b, the uplink signal 25 may interfere with the downlink signal33. Also, when the eNodeB 41 which is receiving the uplink signal 25from the UE 21 d in the small cell 40 receives the downlink signal 33from the eNodeB 31 in the macrocell 30, the downlink signal 33 mayinterfere with the uplink signal 25. Specifically, also in FIG. 5, theinterfering signals are indicated by a dotted line.

FIG. 6 is a diagram for describing a second example of the interferencein a sub-frame in which the link direction is different between amacrocell and a small cell. Referring to FIG. 6, similar to FIG. 5, amacrocell 30 and a small cell 40 are shown. Also, an eNodeB 31, a UE 21c, an eNodeB 41, and a UE 21 d are shown. Here, it is assumed that, insome sub-frame, the link direction is the uplink direction in themacrocell 30, and the link direction is the downlink direction in thesmall cell 40. In this case, when the UE 21 d which is receiving adownlink signal 43 from the eNodeB 41 in the small cell 40 receives anuplink signal 27 from the UE 21 c in the macrocell 30, the uplink signal27 may interfere with the downlink signal 43. Also, when the eNodeB 31which is receiving the uplink signal 27 from the UE 21 c in themacrocell 30 receives the downlink signal 43 from the eNodeB 41 in thesmall cell 40, the downlink signal 43 may interfere with the uplinksignal 27. Specifically, also in FIG. 6, the interfering signals areindicated by a dotted line.

Note that the concept of the small cell 40 encompasses a femtocell,nanocell, picocell, microcell, etc. The small cell 40, which is asupplemental cell for increasing the communication capacity of themacrocell 30, may be introduced by providing an eNodeB which is smallerthan that of a macrocell.

(Dynamic Change in TDD Configuration)

As described above, interference may occur between related cells whendifferent TDD configurations are set for the related cells, and on theother hand, it is desirable that a TDD configuration should bedynamically set for each cell. This is because an improvement inthroughput can be expected by selecting a suitable TDD configurationbased on the uplink or downlink traffic rate in each cell. Specifically,when the uplink traffic rate increases in a cell, a TDD configurationincluding a larger number of uplink sub-frames should be selected basedon the increase in the traffic rate. Also, when the downlink trafficrate increases in a cell, a TDD configuration including a larger numberof downlink sub-frames should be selected based on the increase in thetraffic rate. The characteristics of the traffic rate vary among cells,and therefore, it is desirable that a TDD configuration should bedynamically set for each cell separately. For example, because the radioframe has a length of 10 ms, a TDD configuration may be set every 10 msto several tens of milliseconds.

(Technical Problem)

As described above, interference may occur between related cells whendifferent TDD configurations are set for the related cells, and on theother hand, it is desirable that the link direction TDD configurationshould be dynamically set in order to improve throughput. However, whenthe TDD configuration is dynamically set for each cell (e.g., everyseveral tens of milliseconds), it is considerably difficult to controlthe interference between cells.

Therefore, in this embodiment, in a radio communication system employingTDD, the interference between related cells (e.g., between adjacentcells or between a macrocell and a small cell) can be reduced whileimproving throughput. In the description that follows, specific exampleswill be given in <2. First Embodiment>, <3. Second Embodiment>, <4.Third Embodiment>, and <5. Fourth Embodiment>.

<<2. First Embodiment>>

<2.1. Overview>

Firstly, a first embodiment of the present disclosure will be described.In the first embodiment, the link direction is dynamically set for eachsub-frame of a first frequency band. The link direction is set for eachsub-frame of a second frequency band so that the difference in linkdirection between adjacent cells is reduced, i.e., as large a number ofsub-frames as possible have the same link direction. And, communicationresources of the first frequency band are not allocated to a terminaldevice located in a peripheral portion of a cell. The first embodimentwill now be more specifically outlined with respect to FIG. 7.

FIG. 7 is a diagram for outlining the first embodiment. Referring toFIG. 7, a cell 10 a and a cell 10 b adjacent to the cell 10 a are shown.In this embodiment, the cell 10 is divided into a peripheral portionwhich is further from an eNodeB 100-1 and a central portion (i.e., acentral portion closer to the eNodeB 100-1) other than the peripheralportion. In the central portion of the cell 10, the TDD configuration isdynamically set. On the other hand, in the peripheral portion of thecell 10, the TDD configuration is set to be equal or similar to that ofan adjacent cell. Here, the TDD configuration which is similar to thatof an adjacent cell means a TDD configuration in which the number ofsub-frames which have a link direction different from that of theconfiguration of the adjacent cell is small. For example, theconfiguration 3 and the configuration 4 of FIG. 3 have the same linkdirections in the sub-frames, except for the sub-frame #4, andtherefore, can be said to be similar to each other. Also, for example,in the peripheral portion of the cell 10, the TDD configuration may bestatically or quasi-statically set.

In typical LTE, different TDD configurations cannot be used in a singlefrequency band (i.e., a single component carrier (CC) of 20 MHz), andtherefore, the carrier aggregation technique is used. Carrieraggregation is a technique of aggregating a plurality of CCs, therebyimproving total throughput. For example, when the plurality of CCsinclude a CC 1 and a CC 2, the CC 1 is used as communication resourcesfor a UE 200 which is located in the central portion of the cell 10, andthe CC 2 is used as communication resources for a UE 200 which islocated in the peripheral portion (and the central portion) of the cell10. For the CC 1, the TDD configuration is dynamically set based on thetraffic rate in the cell. For the CC 2, the TDD configuration is set(e.g., statically or quasi-statically) to be equal or similar to that ofan adjacent cell.

By thus setting the TDD configuration and allocating communicationresources, communication resources of a frequency band in which the linkdirection is dynamically set are allocated only to a UE 200 which islocated in the central portion of the cell 10. Therefore, as describedbelow, transmission power of the communication resources can be reduced.As a result, an uplink signal on the communication resources does notsubstantially interfere with a downlink signal of an adjacent cell, anda downlink signal on the communication resources does not substantiallyinterfere with an uplink signal of an adjacent cell. Specifically, in afrequency band in which the link direction is dynamically set,interference such as that shown in FIG. 4 does not substantially occur.Note that only communication resources of a frequency band in which thedifference in link direction from an adjacent cell is small areallocated to a UE 200 which is located in the peripheral portion of thecell 10. Therefore, of course, in the frequency band, interference suchas that shown in FIG. 4 does not substantially occur. Therefore, in aradio communication system employing TDD, by dynamically setting thelink direction, interference between adjacent cells can be reduced whileimproving throughput.

Note that the eNodeB 100-1 allocates small transmission power (e.g.,power 1) to downlink in the CC 1, and large transmission power (e.g.,power 2) to downlink in the CC 2. Also, the eNodeB 100-1 allocates smalltransmission power (e.g., the power 1) to uplink in the CC 1 for a UE200 which is located in the central portion of the cell 10 and for whichcommunication resources of the CC 1 are allocated to uplink. Also, theeNodeB 100-1 allocates large transmission power (e.g., the power 2) touplink in the CC 2 for a UE 200 which is located in the peripheralportion of the cell 10 and for which communication resources of the CC 2are allocated to uplink. This is because transmission power may be smallwhen the distance between the eNodeB 100-1 and a UE 200 is small, andtransmission power needs to be large when the distance is large. Theallocation of the power makes it difficult for a downlink signal anduplink signal of the CC 1 for the central portion of the cell 10 a toreach the central portion of the adjacent cell 10 b. Therefore, asdescribed above, the interference which occurs because different TDDconfigurations are dynamically set for different cells is reduced.

<2.2. Configuration of eNodeB>

An example configuration of the eNodeB 100-1 of the first embodimentwill be described with reference to FIG. 8. FIG. 8 is a block diagramshowing the example configuration of the eNodeB 100-1 of the firstembodiment. Referring to FIG. 8, the eNodeB 100-1 includes a radiocommunication unit 110, a network communication unit 120, a storage unit130, and a processing unit 140.

(Radio Communication Unit 110)

The radio communication unit 110 communicates with one or more UEs 200in the cell 10 over a channel in which the link direction can bedynamically set for each sub-frame which is a unit of time in radiocommunication. The channel includes, for example, at least a firstfrequency band and a second frequency band. The first frequency band andthe second frequency band are each a component carrier. Specifically,the radio communication unit 110 communicates with a UE 200 in the cell10 on the CC 1 and CC 2 in which the link direction can be dynamicallyset for each sub-frame. Also, the radio communication unit 110 transmitsa downlink signal to a UE 200 in the cell 10 and receives an uplinksignal from a UE 200 in the cell 10 according to allocation ofresources. Note that the radio communication unit 110 includes, forexample, an antenna and an RF circuit.

(Network Communication Unit 120)

The network communication unit 120 communicates with communication nodesincluding other eNodeBs. For example, the X2 interface between eNodeBsmay be implemented via the network communication unit 120. The networkcommunication unit 120 may include a radio communication module whichmay be shared by the radio communication unit 110, or a wiredcommunication module, such as a LAN-connected terminal etc.

(Storage Unit 130)

The storage unit 130 stores a program and data for operation of theeNodeB 100-1. The storage unit 130 includes, for example, a medium, suchas a hard disk, a semiconductor memory, etc.

(Processing Unit 140)

The processing unit 140 provides various functions of the eNodeB 100-1.For example, the processing unit 140, which corresponds to a processor,such as a CPU (Central Processing Unit), a DSP (Digital SignalProcessor), etc., executes a program stored in the storage unit 130 oranother storage medium to provide the various functions. The processingunit 140 includes a terminal location measurement unit 141, a trafficrate measurement unit 143, a link direction setting unit 145, a resourcecontrol unit 147, and a power control unit 149.

(Terminal Location Measurement Unit 141)

The terminal location measurement unit 141 measures a location of a UE200 in the cell 10. The location is, for example, represented by adistance between the eNodeB 100-1 and the UE 200. For example, theterminal location measurement unit 141 measures the distance between theeNodeB 100-1 and the UE 200 based on a timing advance value for each UE200.

(Traffic Rate Measurement Unit 143)

The traffic rate measurement unit 143 measures an uplink traffic rateand a downlink traffic rate in the cell 10. The traffic rate measurementunit 143 may measure an actual value of the traffic rate during apredetermined period of time, or may measure an estimated value of thetraffic rate which is predicted to occur during a predetermined periodof time based on a scheduling request from a UE 200 etc. Also, thetraffic rate measurement unit 143 may measure the traffic rate in theperipheral portion of the cell 10 and the traffic rate in the centralportion of the cell 10 separately, or measure the overall traffic ratewithout distinguishing between these transfer rates.

(Link Direction Setting Unit 145)

The link direction setting unit 145 dynamically sets the link directionfor each sub-frame of the first frequency band, and sets the linkdirection for each sub-frame of the second frequency band so that thedifference in link direction between the cell 10 and a cell related tothe cell 10 is reduced. In this embodiment, the related cell is a celladjacent to the cell 10. For example, the link direction setting unit145 dynamically sets the TDD configuration of the CC 1 based on theuplink or downlink traffic rate. As an example, the TDD configuration ofthe CC 1 is set every 10 ms to several tens of milliseconds. Also, thelink direction setting unit 145 sets the TDD configuration of the CC 2to be equal or similar to the TDD configuration of the CC 2 of anadjacent cell. As an example, the link direction setting unit 145negotiates with the eNodeB 100-1 of the adjacent cell, through thenetwork communication unit 120, as to the setting of the link directionof the CC 2, based on the measured traffic rate. The interface betweenthe eNodeB 100-1 of the cell 10 and the eNodeB 100-1 of the adjacentcell is the X2 interface.

Also, the link direction setting unit 145 statically or quasi-staticallysets the link direction for each sub-frame of the second frequency band.For example, the link direction setting unit 145 statically orquasi-statically sets the TDD configuration of the CC 2. As an example,the link direction setting unit 145 sets the TDD configuration of the CC2 each time a predetermined period of time has passed. The predeterminedperiod of time is longer than the interval of the setting of the CC 1.By thus setting statically or quasi-statically, the communication andprocess for adjusting the TDD configuration between eNodeBs can beminimized.

(Resource Control Unit 147)

The resource control unit 147 controls allocation of communicationresources to a UE 200 based on the setting of the link direction of thechannel in which the link direction can be dynamically set for eachsub-frame, and the location of the UE 200 in the cell 10. In particular,in this embodiment, the resource control unit 147 does not allocatecommunication resources of the first frequency band to a UE 200 which islocated in the peripheral portion of the cell 10. For example, theresource control unit 147 does not allocate communication resources ofthe CC 1 to a UE 200 which is located in the peripheral portion of thecell 10, and allocates communication resources of the CC 1 to a UE 200which is not located in the peripheral portion of the cell 10 (i.e., aUE 200 which is located in the central portion of the cell 10). Also,for example, the resource control unit 147 allocates communicationresources of the CC 2 to a UE 200 which is located in the peripheralportion of the cell 10 (and the central portion of the cell 10).

(Power Control Unit 149)

The power control unit 149 controls transmission power in the cell 10.For example, the power control unit 149 controls transmission power ofthe radio communication unit 110. For example, the power control unit149 allocates small transmission power to downlink in the firstfrequency band (e.g., the CC 1), and large transmission power todownlink in the second frequency band (e.g., the CC 2).

Also, for example, the eNodeB 100-1 allocates small transmission powerto uplink in the first frequency band for a UE 200 which is located inthe central portion of the cell 10 and for which communication resourcesof the first frequency band (e.g., the CC 1) are allocated to uplink.Also, the eNodeB 100-1 allocates large transmission power to uplink inthe second frequency band for a UE 200 which is located in theperipheral portion of the cell 10 and for which communication resourcesof the second frequency band (e.g., the CC 2) are allocated to uplink.

<2.3. Configuration of UE>

An example configuration of the UE 200 of the first embodiment will bedescribed with reference to FIG. 9. FIG. 9 is a block diagram showingthe example configuration of the UE 200 of the first embodiment.Referring to FIG. 9, the UE 200 includes a radio communication unit 210,a storage unit 220, and a processing unit 230.

(Radio Communication Unit 210)

The radio communication unit 210 communicates with the eNodeB 100-1 inthe cell 10 over a channel in which the link direction can bedynamically set for each sub-frame which is a unit of time in radiocommunication. Also, the radio communication unit 210 communicates withthe eNodeB 100-1 according to allocation of communication resources tothe radio communication unit 210 itself which is performed by the eNodeB100-1 based on the setting of the link direction of the channel and thelocation of the radio communication unit 210 itself in the cell 10.

For example, the channel includes at least a first frequency band and asecond frequency band. And, the first frequency band and the secondfrequency band are each a component carrier. Specifically, the radiocommunication unit 210 communicates with the eNodeB 100-1 in the cell 10on the CC 1 and CC 2 in which the link direction can be dynamically setfor each sub-frame. Also, the eNodeB 100-1 allocates communicationresources to the UE 200 based on the settings of the TDD configurationsof the CC 1 and CC 2 and the location of the UE 200 in the cell 10, andtherefore, the radio communication unit 210 communicates according tothe allocation of communication resources. Note that the radiocommunication unit 110 includes, for example, an antenna and an RFcircuit.

(Storage Unit 220)

The storage unit 220 stores a program and data for operation of the UE200. The storage unit 220 includes a storage medium, such as a harddisk, a semiconductor memory, etc.

(Processing Unit 230)

The processing unit 230 provides various functions of the UE 200. Forexample, the processing unit 230, which corresponds to a processor, suchas a CPU (Central Processing Unit), a DSP (Digital Signal Processor),etc., executes a program stored in the storage unit 220 or anotherstorage medium to provide the various functions. As an example, theprocessing unit 230 controls communication of the radio communicationunit 210.

For example, the processing unit 230 obtains system information from adownlink signal received by the radio communication unit 210. Also, theprocessing unit 230 recognizes the TDD configuration which has been setfrom the system information. For example, system information of each CCis obtained from the downlink signal of the CC, and the TDDconfiguration of each CC is recognized from the system information ofthe CC. Thereafter, the processing unit 230 causes the radiocommunication unit 210 to communicate based on the recognized TDDconfigurations.

Also, for example, the processing unit 230 obtains schedulinginformation of uplink and downlink from a downlink signal received bythe radio communication unit 210. Also, the processing unit 230recognizes allocation of communication resources to the UE 200 from thescheduling information. Thereafter, the processing unit 230 causes theradio communication unit 210 to communicate according to the allocationof communication resources.

<2.4. Flow of Process>

Next, an example communication control process according to the firstembodiment will be described with reference to FIG. 10. FIG. 10 is aflowchart showing an example schematic flow of the communication controlprocess of the first embodiment. Note that the communication controlprocess is a process in the eNodeB 100-1.

Initially, in step S501, the terminal location measurement unit 141measures the location of a UE 200 in the cell 10. In step S503, thetraffic rate measurement unit 143 measures the uplink traffic rate andthe downlink traffic rate in the cell 10. Thereafter, in step S505, thelink direction setting unit 145 sets the link direction (e.g., the TDDconfiguration) of the CC 1 based on the measured traffic rates.

In step S507, the link direction setting unit 145 determines whether ornot a predetermined period of time has passed. If the predeterminedperiod of time has passed, control proceeds to step S509. Otherwise,control proceeds to step S513.

In step S509, the link direction setting unit 145 negotiates with theeNodeB 100-1 of an adjacent cell, through the network communication unit120, as to the setting of the link direction of the CC 2, based on themeasured traffic rates. Thereafter, in step S511, the link directionsetting unit 145 sets the link direction (i.e., the TDD configuration)of the CC 2 based on the result of the negotiation with the eNodeB 100-1of the adjacent cell.

In step S513, the resource control unit 147 allocates communicationresources of the CC 2 to a UE 200 which is located in the peripheralportion of the cell 10 (and the central portion of the cell 10). In stepS515, the resource control unit 147 allocates communication resources ofthe CC 1 to a UE 200 which is not located in the peripheral portion ofthe cell 10 (i.e., a UE 200 which is located in the central portion ofthe cell 10).

In step S517, the radio communication unit 110 communicates with the UE200 using the allocated communication resources.

<2.5. Variations>

(1) Overview

Next, a variation of the first embodiment will be described. In thisvariation, the cell 10 is a macrocell which covers all or part of asmall cell. The eNodeB 100-1 causes a communication node (e.g., aneNodeB) of the small cell to set the link direction for each sub-framein the small cell so that the difference in link direction between thecell 10 and the small cell is reduced. Such a variation of the firstembodiment will now be more specifically outlined with reference to FIG.11.

FIG. 11 is a diagram for outlining the variation of the firstembodiment. Referring to FIG. 11, a cell 10 which is a macrocell and twosmall cells 40 are shown. The cell 10 is similar to that which has beendescribed with reference to FIG. 7. Specifically, in the cell 10, the CC1 is used as communication resources for a UE 200 which is located inthe central portion of the cell 10, and the CC 2 is used ascommunication resources for a UE 200 which is located in the peripheralportion (and the central portion) of the cell 10. The small cell 40 a islocated in the peripheral portion of the cell 10, and the small cell 40b is located in the central portion of the cell 10.

In such a case, for example, the eNodeB 100-1 causes an eNodeB 41 a toset the TDD configuration of the CC 2 of the small cell 40 a to be equalor similar to the TDD configuration of the CC 2 of the cell 10. Also,the eNodeB 100-1 causes an eNodeB 41 b to set the TDD configuration ofthe CC 1 of the small cell 40 b to be equal or similar to the TDDconfiguration of the CC 1 of the cell 10.

By thus setting the TDD configuration, the link direction of the cell 10which is a macrocell is equal to the link direction of the small cell 40in most of the sub-frames. Therefore, the interference described withreference to FIGS. 5 and 6 can be reduced.

(Variation of Small Cell)

Note that, similar to the cell 10, the small cell 40 may be divided intoa peripheral portion which is further from the eNodeB 41 and a centralportion (i.e., a central portion closer to the eNodeB 41) other than theperipheral portion. This will now be more specifically described withreference to FIG. 12.

FIG. 12 is a diagram for describing operations of the eNodeB 41 and a UE200 in the small cell 40. Referring to FIG. 12, the small cells 40 a and40 b shown in FIG. 11 are also shown. In this case, the eNodeB 41 a ofthe small cell 40 a dynamically sets the link direction for eachsub-frame of a CC which is different from the CC 2, and does notallocate communication resources of the different frequency band to anUE 200 e which is located in the peripheral portion of the small cell 40a. The eNodeB 41 a allocates communication resources of the differentfrequency band to a UE 200 f which is located in the central portion ofthe small cell 40 a. Also, the eNodeB 41 b of the small cell 40 bdynamically sets the link direction for each sub-frame of a CC otherthan the CC 1, and does not allocate communication resources of thedifferent frequency band to a UE 200 g which is located in theperipheral portion of the small cell 40 b. The eNodeB 41 b allocatescommunication resources of the different frequency band to a UE 200 hwhich is located in the central portion of the small cell 40 b.

By thus allocating resources, communication resources of a frequencyband for which the link direction is dynamically set (i.e., thedifferent frequency band) are allocated only to a UE 200 which islocated in the central portion of the small cell 40. Therefore, in thesmall cell, transmission power of the communication resources can bereduced. As a result, an uplink signal on the communication resources ofthe small cell does not substantially interfere with a downlink signalof the cell 10, and a downlink signal on the communication resources ofthe small cell does not substantially interfere with an uplink signal ofthe macrocell. Specifically, in a frequency band for which the linkdirection is dynamically set, interference of a small cell with amacrocell, such as those shown in FIGS. 5 and 6, does not substantiallyoccur.

Moreover, the distance between a UE 200 which is located in the centralportion of the small cell 40, and the eNodeB 41, is smaller than thedistance between the eNodeB 100-1 and the eNodeB 41, and therefore, adownlink signal of the cell 10 does not substantially interfere with anuplink signal of the small cell 40. Also, the distance between a UE 200which is located in the central portion of the small cell 40, and theeNodeB 41, is smaller than the distance between the UE 200 and anotherUE 200 which communicates with the eNodeB 100-1, and therefore, anuplink signal of the cell 10 does not substantially interfere with adownlink signal of the small cell 40. Specifically, in a frequency bandfor which the link direction is dynamically set, interference of a smallcell with a macrocell, such as those shown in FIGS. 5 and 6, does notsubstantially occur.

Note that, in the small cell 40, only communication resources of afrequency band (the CC 1 or the CC 2) for which the difference in linkdirection from the cell 10 is small are allocated to a UE 200 which islocated in the peripheral portion of the small cell 40. Therefore, inthe frequency band, interference, such as those shown in FIGS. 5 and 6,does not substantially occur.

Therefore, in a radio communication system employing TDD, by dynamicallysetting the link direction, interference between a macrocell and a smallcell can be reduced while improving throughput.

(2) Configuration of eNodeB

In this variation, the link direction setting unit 145 and the powercontrol unit 149 of the eNodeB 100-1 which have been described withreference to FIG. 8 further operate as follows. Note that, as describedabove, in this variation, the cell 10 is a macrocell which covers all orpart of the small cell 40.

(Link Direction Setting Unit 145)

The link direction setting unit 145 causes the eNodeB 41 in the smallcell 40 to set the link direction for each sub-frame in the small cell40 so that the difference in link direction between the cell 10 and thesmall cell 40 is reduced. Specifically, the link direction setting unit145 causes the eNodeB 41 to set the TDD configuration of the small cell40 to be equal or similar to the TDD configuration of the cell 10.

For example, the link direction setting unit 145, when the small cell 40is located in the peripheral portion of the cell 10, causes the eNodeB41 to set the link direction of the second frequency band in the smallcell 40 so that the difference in link direction between the cell 10 andthe small cell 40 is reduced. Specifically, the link direction settingunit 145 causes the eNodeB 41 a to set the TDD configuration of the CC 2in the small cell 40 a to be equal or similar to the TDD configurationof the CC 2 of the cell 10. In this case, for example, similar to theTDD configuration of the CC 2 of the cell 10, the TDD configuration ofthe CC 2 in the small cell 40 a is statically or quasi-statically set.

Also, for example, the link direction setting unit 145, when the smallcell 40 is not located in the peripheral portion of the cell 10, causesthe eNodeB 41 to set the link direction of the first frequency band inthe small cell 40 so that the difference in link direction between thecell 10 and the small cell 40 is reduced. Specifically, the linkdirection setting unit 145 causes the eNodeB 41 b to set the TDDconfiguration of the CC 1 in the small cell 40 b to be equal or similarto the TDD configuration of the CC 1 of the cell 10. In this case, forexample, similar to the TDD configuration of the CC 1 of the cell 10,the TDD configuration of the CC 1 in the small cell 40 b is dynamicallyset.

As a specific technique of controlling the eNodeB 41, the link directionsetting unit 145 notifies the eNodeB 41 of the link direction for eachsub-frame of the first frequency band or the link direction for eachsub-frame of the second frequency band, which has been set by the linkdirection setting unit 145. As a result, the link direction setting unit145 causes the eNodeB 41 to set the link direction for each sub-frame inthe small cell 40. The link direction setting unit 145 performs thenotification of the eNodeB 41, for example, through the networkcommunication unit 120.

Note that, as described above with reference to FIG. 12, the eNodeB 41,when the small cell 40 is located in the peripheral portion of the cell10, may dynamically set the link direction for each sub-frame of afrequency band which is different from the second frequency band, andmay not allocate communication resources of the different frequency bandto a UE 200 which is not located in the peripheral portion of the smallcell 40. Specifically, the eNodeB 41 may dynamically set the TDDconfiguration of a CC which is different from the CC 2, and may notallocate communication resources of the different CC to a UE 200 e whichis located in the peripheral portion of the small cell 40 a.

Similarly, as described above with reference to FIG. 12, the eNodeB 41,when the small cell 40 is not located in the peripheral portion of thecell 10, may dynamically set the link direction for each sub-frame of afrequency band which is different from the first frequency band, and maynot allocate communication resources of the different frequency band toa terminal device which is located in the peripheral portion of thesmall cell 40. Specifically, the eNodeB 41 may dynamically set the TDDconfiguration of a CC which is different from the CC 1, and may notallocate communication resources of the different CC to a UE 200 g whichis located in the peripheral portion of the small cell 40 b.

(Power Control Unit 149)

The power control unit 149 may reduce transmission power in the cell 10for a sub-frame in which the link direction in the cell 10 is differentfrom the link direction in the small cell 40. For example, the powercontrol unit 149 reduces transmission power of the CC 2 in the cell 10for a sub-frame in which the link direction of the CC 2 in the cell 10is different from the link direction of the CC 2 in the small cell 40 a.Also, for example, the power control unit 149 reduces transmission powerof the CC 1 in the cell 10 for a sub-frame in which the link directionof the CC 1 in the cell 10 is different from the link direction of theCC 1 in the small cell 40 b. In this case, for example, the powercontrol unit 149 is notified of the link direction (i.e., the TDDconfiguration) in the small cell 40, by the eNodeB 41 through thenetwork communication unit 120.

By thus reducing transmission power, interference of a downlink signalof the cell 10 with an uplink signal of the small cell 40, andinterference of an uplink signal of the cell 10 with a downlink signalof the small cell 40, can be reduced.

(Others)

Note that if the number of sub-frames which can be used in communicationin the small cell 40 is limited, sub-frames to be used in communicationmay be selected based on the downlink or uplink traffic rate in thesmall cell 40. Specifically, the ratio of uplink sub-frames and downlinksub-frames in a radio frame may be changed, depending on the downlink oruplink traffic rate. This will now be specifically described withreference to FIG. 13.

FIG. 13 is a diagram for describing example selection of sub-frames usedin communication in a small cell. Referring to FIG. 13, a CC 1 which isused as communication resources for a UE 200 which is located in thecentral portion of a cell 10 is set to have a TDD configurationcorresponding to the configuration 1 of FIG. 3. Also, a CC 2 which isused as communication resources for a UE 200 which is located in theperipheral portion of the cell 10 is set to have a TDD configurationcorresponding to the configuration 3 of FIG. 3.

In a small cell 40 a which is located in the peripheral portion of thecell 10, the downlink traffic rate is higher than the uplink trafficrate, and therefore, a larger number of downlink sub-frames are selectedas sub-frames to be used in communication. On the other hand, in a smallcell 40 c which is located in the peripheral portion of the cell 10, theuplink traffic rate is higher than the downlink traffic rate, andtherefore, a larger number of uplink sub-frames are selected assub-frames to be used in communication.

Similarly, in a small cell 40 b which is located in the central portionof the cell 10, the downlink traffic rate is higher than the uplinktraffic rate, and therefore, a larger number of downlink sub-frames areselected as sub-frames to be used in communication. On the other hand,in a small cell 40 d which is located in the central portion of the cell10, the uplink traffic rate is higher than the downlink traffic rate,and therefore, a larger number of uplink sub-frames are selected assub-frames to be used in communication.

(3) Flow of Process

Next, an example communication control process according to a variationof the first embodiment will be described with reference to FIG. 14.FIG. 14 is a flowchart showing an example schematic flow of thecommunication control process of the variation of the first embodiment.The communication control process is a process in an eNodeB 100-1. Here,only step S521 will be described which is the difference between theexample communication control process of the first embodiment describedwith reference to FIG. 10 and the example communication control processof the variation.

In step S521, the link direction setting unit 145 notifies an eNodeB 41of the link direction for each sub-frame of the CC 1 or the linkdirection for each sub-frame of the CC 2, that has been set by the linkdirection setting unit 145. As a result, the link direction setting unit145 causes the eNodeB 41 to set the link direction for each sub-frame inthe small cell 40. The link direction setting unit 145 performs thenotification of the eNodeB 41, for example, through the networkcommunication unit 120.

<<3. Second Embodiment>

<3.1. Overview>

The first embodiment has been particularly described with reference toan operation of an eNodeB in a cell adjacent to another cell. Moreover,a variation of the first embodiment has been particularly described withreference to an operation of an eNodeB in a macrocell in a case wherethe cell adjacent to another cell is the macrocell. Next, a secondembodiment of the present disclosure will be particularly described withreference to an operation of an eNodeB in a small cell which covers allor part of a macrocell. In the second embodiment, in the small cell, thelink direction is dynamically set for each sub-frame of a firstfrequency band, and the link direction is set for each sub-frame of asecond frequency band so that the difference in link direction betweenthe small cell and the macrocell is reduced, i.e., as large a number ofsub-frames as possible have the same link direction. And, communicationresources of the first frequency band are not allocated to a terminaldevice which is located in the peripheral portion of the small cell. Thesecond embodiment will now be more specifically outlined with referenceto FIGS. 15 and 16.

FIGS. 15 and 16 are diagrams for outlining the second embodiment.Referring to FIG. 15, a macrocell 30 and a cell 10 which is a small cellare shown. An eNodeB 100-2 according to this embodiment is an eNodeB inthe small cell. Referring to FIG. 16, the cell 10 which is a small cellis shown in greater detail. In this embodiment, the cell 10 is dividedinto a peripheral portion which is further from the eNodeB 100-2 and acentral portion (i.e., a central portion closer to the eNodeB 100-2)other than the peripheral portion. And, in the central portion of thecell 10, the TDD configuration is dynamically set. On the other hand, inthe peripheral portion of the cell 10, the TDD configuration is set tobe equal or similar to that of the macrocell. Also, for example, in theperipheral portion of the cell 10, the TDD configuration is staticallyor quasi-statically set.

For example, in the cell 10 which is a small cell, the carrieraggregation technique of aggregating a plurality of cells is used. Whenthe plurality of CCs include a CC 1 and a CC 2, the CC 1 is used ascommunication resources for a UE 200 which is located in the centralportion of the cell 10, and the CC 2 is used as communication resourcesfor a UE 200 which is located in the peripheral portion (and the centralportion) of the cell 10. For the CC 1, the TDD configuration isdynamically set based on the traffic. For the CC 2, the TDDconfiguration is set (e.g., statically or quasi-statically) to be equalor similar to that of the macrocell.

By thus setting the TDD configuration and allocating communicationresources, in the cell 10 communication resources of a frequency band inwhich the link direction is dynamically set are allocated only to a UE200 which is located in the central portion of the cell 10 which is asmall cell. Therefore, in the cell 10, transmission power of thecommunication resources can be reduced. As a result, an uplink signal onthe communication resources of the cell 10 does not substantiallyinterfere with a downlink signal of the macrocell 30, and a downlinksignal on the communication resources of the cell 10 does notsubstantially interfere with an uplink signal of the macrocell 30.Specifically, in a frequency band in which the link direction isdynamically set, interference of a small cell with a macrocell, such asthose shown in FIGS. 5 and 6, does not substantially occur.

Moreover, the distance between a UE 200 which is located in the centralportion of the cell 10 which is a small cell, and the eNodeB 100-2, issmaller than the distance between an eNodeB 31 and the eNodeB 100-2, andtherefore, a downlink signal of the macrocell 30 does not substantiallyinterfere with an uplink signal of the cell 10. Also, the distancebetween a UE 200 which is located in the central portion of the cell 10which is a small cell, and the eNodeB 100-2, is smaller than thedistance between that UE 200 and a UE 200 which communicates with theeNodeB 31, and therefore, an uplink signal of the macrocell 30 does notsubstantially interfere with a downlink signal of the cell 10.Specifically, in a frequency band in which the link direction isdynamically set, interference of a macrocell with a small cell, such asthose shown in FIGS. 5 and 6, does not substantially occur.

Note that, in the cell 10 which is a small cell, only communicationresources of a frequency band (the CC 2) in which the difference in linkdirection from the macrocell 30 is small are allocated to a UE 200 whichis located in the peripheral portion of the cell 10. Therefore, in thefrequency band, interference, such as those of FIGS. 5 and 6, does notsubstantially occur.

Therefore, in a radio communication system employing TDD, by dynamicallysetting the link direction, interference between a macrocell and a smallcell can be reduced while improving throughput.

<3.2. Configuration of eNodeB

An example configuration of the eNodeB 100-2 of the second embodimentwill be described with reference to FIG. 17. FIG. 17 is a block diagramshowing the example configuration of the eNodeB 100-2 of the secondembodiment. Referring to FIG. 17, the eNodeB 100-2 includes a radiocommunication unit 110, a network communication unit 120, a storage unit130, and a processing unit 150.

Here, the radio communication unit 110, the network communication unit120, and the storage unit 130 are not different between the firstembodiment and the second embodiment. Also, in the processing unit 150,the terminal location measurement unit 141, the traffic rate measurementunit 143, and the resource control unit 147 are not different betweenthe first embodiment and the second embodiment. Therefore, here, a linkdirection setting unit 155 and a power control unit 159 will bedescribed.

(Link Direction Setting Unit 155)

The link direction setting unit 155 dynamically sets the link directionfor each sub-frame of the first frequency band, and sets the linkdirection for each sub-frame of the second frequency band so that thedifference in link direction between the cell 10 and a cell related tothe cell 10 is reduced. In this embodiment, the cell 10 is a small cell,and the related cell is a macrocell 30 which covers all or part of thecell 10. For example, the link direction setting unit 155 dynamicallysets the TDD configuration of the CC 1 based on the uplink or downlinktraffic rate. As an example, the TDD configuration of the CC 1 is setevery 10 ms to several tens of milliseconds. Also, the link directionsetting unit 155 sets the TDD configuration of the CC 2 to be equal orsimilar to the TDD configuration of the CC 2 of the macrocell 30. As anexample, the link direction setting unit 155 is notified of the TDDconfiguration of the CC 2 of the macrocell 30 by the eNodeB 31 throughthe network communication unit 120.

Note that, in the macrocell 30, communication resources of a frequencyband corresponding to the location of a UE 200 may be allocated to theUE 200. In this case, if the cell 10 is located in the peripheralportion of the macrocell 30, the second frequency band (e.g., the CC 2)may be a frequency band which is allocated to a UE 200 which is locatedin the peripheral portion of the macrocell 30. Also, if the cell 10 isnot located in the peripheral portion of the macrocell 30 (i.e., thecell 10 is located in the central portion), the second frequency bandmay be a frequency band which is allocated to a UE 200 which is notlocated in the peripheral portion of the macrocell 30 (i.e., a UE 200which is located in the central portion).

(Power Control Unit 159)

The power control unit 159 controls transmission power in the cell 10.For example, the power control unit 159 controls transmission power ofthe radio communication unit 110. For example, the power control unit159 allocates small transmission power to downlink in the firstfrequency band (e.g., the CC 1), and large transmission power todownlink in the second frequency band (e.g., the CC 2).

Also, for example, the eNodeB 100-2 causes a UE 200 which is located inthe central portion of the cell 10 and in which communication resourcesof the first frequency band (e.g., the CC 1) are allocated to uplink toallocate small transmission power to uplink in the first frequency band.Also, the eNodeB 100-1 causes a UE 200 which is located in theperipheral portion of the cell 10 and in which communication resourcesof the second frequency band (e.g., the CC 2) are allocated to uplink toallocate large transmission power to uplink in the second frequencyband.

Note that the power control unit 159 may request the eNodeB 31 of themacrocell 30 to reduce transmission power in the macrocell 30 in asub-frame in which the link direction of the second frequency band inthe cell 10 is different from the link direction of the second frequencyband in the macrocell 30. For example, the power control unit 159notifies the eNodeB 31, through the network communication unit 120, of asub-frame in which the link direction of the CC 2 in the cell 10 isdifferent from the link direction of the CC 2 in the macrocell 30. Bythus reducing transmission power in the macrocell 30, interference of adownlink signal in the macrocell 30 with an uplink signal in the cell10, and interference of an uplink signal of the macrocell 30 with adownlink signal of the cell 10, can be further reduced.

<3.3. Flow of Process>

Next, an example communication control process according to the secondembodiment will be described with reference to FIG. 18. FIG. 18 is aflowchart showing an example schematic flow of the communication controlprocess of the second embodiment. The communication control process is aprocess in the eNodeB 100-2. Steps S501-S505 and S511-S517 of thecommunication control process of the first embodiment described withreference to FIG. 10 correspond to steps S601-S605 and S611-S617 of thecommunication control process of the second embodiment. Therefore, here,only step S607 will be described which is the difference between theexample communication control process of the first embodiment describedwith reference to FIG. 10 and the example communication control processof the second embodiment.

In step S607, the link direction setting unit 155 determines whether ornot the link direction setting unit 155 itself has been notified of thelink direction (i.e., the TDD configuration) of the CC 2 of themacrocell 30 by the eNodeB 31 through the network communication unit120. If the link direction setting unit 155 has been notified of thelink direction, control proceeds to step S611. Otherwise, controlproceeds to step S613.

<<4. Third Embodiment>>

<4.1. Overview>

Next, a third embodiment of the present disclosure will be described. Inthe third embodiment, communication resources in a sub-frame in whichthe link direction in a cell is different from the link direction in acell adjacent to that cell are not allocated to a terminal device whichis located in the peripheral portion of that cell. The third embodimentwill now be more specifically described with reference to FIG. 19.

FIG. 19 is a diagram for outlining the third embodiment. Referring toFIG. 19, a cell 10 a and a cell 10 b adjacent to the cell 10 a areshown. In the cell 10 a and the cell 10 b, the link direction (i.e., theTDD configuration) is dynamically set for each sub-frame. As an example,in some radio frame, in the cell 10 a, a TDD configuration correspondingto the configuration 0 of FIG. 3 is set for each frequency band. Also,in the same radio frame, in the cell 10 b, a TDD configurationcorresponding to the configuration 6 of FIG. 3 is set for each frequencyband. In this case, a sub-frame in which the link direction of the cell10 a is different from the link direction of the cell 10 b is thesub-frame #9. Therefore, while interference such as that shown in FIG. 4does not occur in the sub-frames #0-#8, interference such as that shownin FIG. 4 occurs in the sub-frame #9. Therefore, in this embodiment,while communication resources in the sub-frames #0-8 may be allocated toany UE 200, communication resources in the sub-frame #9 are notallocated to a UE 200 which is located in the peripheral portion of thecell 10. Specifically, communication resources in the sub-frame #9 areallocated only to a UE 200 which is located in the central portion ofthe cell 10.

By thus allocating communication resources, communication resources areallocated only to a UE 200 which is located in the central portion ofthe cell 10, in a sub-frame of a radio frame in which the link directionis different between adjacent cells. Therefore, transmission power inthe sub-frame can be reduced. As a result, in the sub-frame, an uplinksignal of the cell 10 does not substantially interfere with a downlinksignal of an adjacent cell, and a downlink signal of the cell 10 doesnot substantially interfere with an uplink signal of an adjacent cell.Specifically, even in a sub-frame in which the link direction isdifferent between adjacent cells, interference such as that shown inFIG. 4 does not substantially occur. Also, of course, even in asub-frame of a radio frame in which the link direction is the samebetween adjacent cells, interference such as that shown in FIG. 4 doesnot substantially occur. Therefore, in a radio communication systememploying TDD, by dynamically setting the link direction, interferencebetween adjacent cells can be reduced while improving throughput.

<4.2. Configuration of eNodeB>

An example configuration of an eNodeB 100-3 according to the thirdembodiment will be described with reference to FIG. 20. FIG. 20 is ablock diagram showing the example configuration of the eNodeB 100-3 ofthe third embodiment. Referring to FIG. 20, the eNodeB 100-3 includes aradio communication unit 110, a network communication unit 120, astorage unit 130, and a processing unit 160.

Here, the radio communication unit 110, the network communication unit120, and the storage unit 130 are not different between the firstembodiment and the third embodiment. Also, in the processing unit 160,the terminal location measurement unit 141 and the traffic ratemeasurement unit 143 are not different between the first embodiment andthe third embodiment. Therefore, here, a link direction setting unit165, a resource control unit 167, and a power control unit 169 will bedescribed.

(Link Direction Setting Unit 165)

The link direction setting unit 165 dynamically sets the link directionfor each sub-frame of one or more frequency bands. For example, the oneor more frequency bands include a CC 1 and a CC 2. The link directionsetting unit 165 dynamically sets any of the TDD configurations of FIG.3 for the CC 1 and the CC 2 based on the uplink or downlink trafficrate. As an example, the TDD configuration is set every 10 ms to severaltens of milliseconds. For the CC 1 and the CC 2, the same TDDconfiguration may be set, or different TDD configurations may be set.

Also, the link direction setting unit 165 notifies an adjacent cell ofthe link direction (i.e., the TDD configuration) in the cell 10, forexample, through the network communication unit 120.

(Resource Control Unit 167)

The resource control unit 167 controls allocation of communicationresources to a UE 200 based on the setting of the link direction of achannel in which the link direction can be dynamically set for eachsub-frame, and the location of the UE 200 in the cell 10. In particular,in this embodiment, the resource control unit 167 does not allocatecommunication resources in a sub-frame in which the link direction inthe cell 10 is different from the link direction in a cell related tothe cell 10, to a UE 200 which is located in the peripheral portion ofthe cell 10. The related cell is a cell adjacent to the cell 10. Forexample, when the sub-frame in which the link direction is differentbetween the cell 10 and the adjacent cell is the sub-frame #9, theresource control unit 167 does not allocate communication resources inthe sub-frame #9 to a UE 200 which is located in the peripheral portionof the cell 10. Specifically, the resource control unit 167 allocatescommunication resources in the sub-frame #9 only to a UE 200 which islocated in the central portion of the cell 10. Also, the resourcecontrol unit 167 allocates communication resources in the sub-frames#0-8 to a UE 200 which is located in the peripheral portion of the cell10 and a UE 200 which is located in the central portion of the cell 10.

Note that the resource control unit 167 is notified of the linkdirection (i.e., the TDD configuration) in the adjacent cell by theeNodeB 100-3 in the adjacent cell.

(Power Control Unit 169)

The power control unit 169 controls transmission power in the cell 10.For example, the power control unit 169 reduces transmission power inthe cell 10, in a sub-frame in which the link direction in the cell 10is different from the link direction in a cell adjacent to the cell 10.More specifically, the power control unit 169 allocates smalltransmission power to downlink. Also, the power control unit 169 causesa UE 200 which is located in the central portion of the cell 10 toallocate small transmission power to uplink.

<4.4. Flow of Process>

Next, an example communication control process according to the thirdembodiment will be described with reference to FIG. 21. FIG. 21 is aflowchart showing an example schematic flow of the communication controlprocess of the third embodiment. Note that the communication controlprocess is a process in the eNodeB 100-3.

Initially, in step S701, the terminal location measurement unit 141measures the location of a UE 200 in the cell 10. Also, in step S703,the traffic rate measurement unit 143 measures the uplink traffic rateand the downlink traffic rate in the cell 10.

In step S705, the link direction setting unit 165 sets the linkdirection (i.e., the TDD configuration) for each sub-frame based on themeasured traffic rates. Also, in step S707, the link direction settingunit 165 notifies an adjacent cell of the link direction in the cell 10,for example, through the network communication unit 120. Also, in stepS709, the resource control unit 167 is notified of the link direction(i.e., the TDD configuration) in the adjacent cell by the adjacent cell.

In step S711, the resource control unit 167 allocates communicationresources in a sub-frame in which the link direction in the cell 10 isdifferent from the link direction in a cell adjacent to the cell 10, toa UE 200 which is not located in the peripheral portion of the cell 10(i.e., a UE 200 which is located in the central portion of the cell 10).Also, in step S713, the resource control unit 167 allocatescommunication resources in a sub-frame in which the link direction inthe cell 10 is the same as the link direction in a cell adjacent to thecell 10, to a UE 200 which is located in the cell 10.

In step S715, the radio communication unit 110 communicates with the UE200 using the allocated communication resources.

<<5. Fourth Embodiment>>

<5.1. Overview>

The third embodiment has been particularly described with reference toan operation of an eNodeB in a cell adjacent to another cell. Next, afourth embodiment of the present disclosure will be particularlydescribed with reference to an operation of an eNodeB in a small cellwhich covers all or part of a macrocell. In the fourth embodiment,communication resources in a sub-frame in which the link direction in asmall cell is different from the link direction in a macrocell whichcovers all or part of the small cell, are not allocated to a terminaldevice which is located in the peripheral portion of the small cell, inthe small cell. The fourth embodiment will now be more specificallyoutlined with reference to FIG. 22.

FIG. 22 is a diagram for outlining the fourth embodiment. Referring toFIG. 22, a cell 10 which is a small cell, and a macrocell 30 whichcovers all or part of the cell 10, are shown. In the cell 10, the linkdirection (i.e., the TDD configuration) is dynamically set for eachsub-frame. On the other hand, in the macrocell 30, the link direction(i.e., the TDD configuration) may be dynamically, or alternativelystatically or quasi-statically, set for each sub-frame. As an example,in some radio frame, in the cell 10, in each frequency band, a TDDconfiguration corresponding to the configuration 6 of FIG. 3 is set.Also, in the same radio frame, in the macrocell 30, in each frequencyband, a TDD configuration corresponding to the configuration 0 of FIG. 3is set. In this case, a sub-frame in which the link direction in thecell 10 is different from the link direction in the macrocell 30 is thesub-frame #9. Therefore, while interference such as those shown in FIGS.5 and 6 does not occur in the sub-frames #0-#8, interference such asthose shown in FIGS. 5 and 6 may occur in the sub-frame #9. Therefore,in this embodiment, in the cell 10, while communication resources in thesub-frames #0-8 are allocated to any UE 200, communication resources inthe sub-frame #9 are not allocated to a UE 200 which is located in theperipheral portion of the cell 10. Specifically, in the cell 10,communication resources in the sub-frame #9 are allocated only to a UE200 which is located in the central portion of the cell 10.

By thus allocating communication resources, communication resources areallocated only to a UE 200 which is located in the central portion ofthe cell 10, in the cell 10, in a sub-frame of a radio frame in whichthe link direction is different between the cell 10 which is a smallcell and the macrocell 30. Therefore, in the cell 10, transmission powerin the sub-frame can be reduced. As a result, in the sub-frame, anuplink signal of the cell 10 does not substantially interfere with adownlink signal of the macrocell 30, and a downlink signal of the cell10 does not substantially interfere with an uplink signal of themacrocell 30. Specifically, even in a sub-frame in which the linkdirection is different between adjacent cells, interference of a smallcell with a macrocell, such as those shown in FIGS. 5 and 6, does notsubstantially occur.

Moreover, the distance between a UE 200 which is located in the centralportion of the cell 10 which is a small cell and an eNodeB 100-4 issmaller than the distance between an eNodeB 31 and the eNodeB 100-4, andtherefore, a downlink signal of the macrocell 30 does not substantiallyinterfere with an uplink signal of the cell 10. Also, the distancebetween a UE 200 which is located in the central portion of the cell 10and the eNodeB 100-4 is smaller than the distance between that UE 200and a UE 200 which communicates with the eNodeB 31, and therefore, anuplink signal of the macrocell 30 does not substantially interfere witha downlink signal of the cell 10. Specifically, even in a sub-frame inwhich the link direction is different between adjacent cells,interference of a macrocell with a small cell, such as those shown inFIGS. 5 and 6, does not substantially occur.

Also, of course, even in a sub-frame of a radio frame in which the linkdirection is the same between the cell 10 and the macrocell 30,interference such as those shown in FIGS. 5 and 6 does not occur.

Therefore, in a radio communication system employing TDD, by dynamicallysetting the link direction, interference between adjacent cells can bereduced while improving throughput.

<5.2. Configuration of eNodeB>

An example configuration of the eNodeB 100-4 of the fourth embodimentwill be described with reference to FIG. 23. FIG. 23 is a block diagramshowing an example configuration of the eNodeB 100-4 of the fourthembodiment. Referring to FIG. 23, the eNodeB 100-4 includes a radiocommunication unit 110, a network communication unit 120, a storage unit130, and a processing unit 170.

Here, the radio communication unit 110, the network communication unit120, and the storage unit 130 are not different between the thirdembodiment and the fourth embodiment. Also, even in the processing unit170, the terminal location measurement unit 141, the traffic ratemeasurement unit 143, and the link direction setting unit 165 are notdifferent between the third embodiment and the fourth embodiment.Therefore, here, a resource control unit 177 and a power control unit179 will be described.

(Resource Control Unit 177)

The resource control unit 177 controls allocation of communicationresources to a UE 200 based on the setting of the link direction of achannel in which the link direction can be dynamically set for eachsub-frame, and the location of the UE 200 in the cell 10. In particular,in this embodiment, the resource control unit 177 does not allocatecommunication resources in a sub-frame in which the link direction inthe cell 10 is different from the link direction in a cell related tothe cell 10, to a UE 200 which is located in the peripheral portion ofthe cell 10. Here, the cell 10 is a small cell, and the related cell isa macrocell which covers all or part of the cell 10. For example, whenthe sub-frame in which the link direction is different between the cell10 and the macrocell 30 is the sub-frame #9, the resource control unit177 does not allocate communication resources in the sub-frame #9 to aUE 200 which is located in the peripheral portion of the cell 10.Specifically, the resource control unit 177 allocates communicationresources in the sub-frame #9 only to a UE 200 which is located in thecentral portion of the cell 10. Also, the resource control unit 167allocates communication resources in the sub-frames #0-8 to a UE 200which is located in the peripheral portion of the cell 10 and a UE 200which is located in the central portion of the cell 10.

Note that the resource control unit 177 is notified of the linkdirection (i.e., the TDD configuration) in the macrocell 30 by theeNodeB 31 of the macrocell 30.

(Power Control Unit 179)

The power control unit 179 controls transmission power in the cell 10.For example, the power control unit 179 reduces transmission power inthe cell 10, in a sub-frame in which the link direction in the cell 10is different from the link direction in the macrocell 30. Morespecifically, the power control unit 179 allocates small transmissionpower to downlink. Also, the power control unit 179 causes a UE 200which is located in the central portion of the cell 10 to allocate smalltransmission power to uplink.

Note that the power control unit 179 may request the eNodeB 31 of themacrocell 30 to reduce transmission power in the macrocell 30 in asub-frame in which the link direction in the cell 10 is different fromthe link direction in the macrocell 30. For example, the power controlunit 179 notifies the eNodeB 31, through the network communication unit120, of a sub-frame in which the link direction in the cell 10 isdifferent from the link direction in the macrocell 30. By thus reducingtransmission power in the macrocell 30, interference of a downlinksignal of the macrocell 30 with an uplink signal of the cell 10, andinterference of an uplink signal of the macrocell 30 with a downlinksignal of the cell 10, can be further reduced.

<5.3. Flow of Process>

Next, an example communication control process according to the fourthembodiment will be described with reference to FIG. 24. FIG. 24 is aflowchart showing an example schematic flow of the communication controlprocess of the fourth embodiment. Note that the communication controlprocess is a process in the eNodeB 100-4. Steps S701-S705 and S715 ofthe communication control process of the third embodiment described withreference to FIG. 21 correspond to steps S801-S805 and S815 of thecommunication control process of the fourth embodiment, respectively.Therefore, here, only steps S807, S811, and S813 will be described whichis the difference between the example communication control process ofthe third embodiment described with reference to FIG. 21 and the examplecommunication control process of the fourth embodiment.

In step S807, the resource control unit 177 is notified of the linkdirection (i.e., the TDD configuration) in the macrocell 30 by theeNodeB 31 of the macrocell 30.

In step S811, the resource control unit 177 allocates communicationresources in a sub-frame in which the link direction in the cell 10 isdifferent from the link direction in the macrocell 30 to a UE 200 whichis not located in the peripheral portion of the cell 10 (i.e., a UE 200which is located in the central portion of the cell 10). Also, in stepS813, the resource control unit 177 allocates communication resources ina sub-frame in which the link direction in the cell 10 is the same asthe link direction in the macrocell 30 to a UE 200 which is located inthe cell 10.

<<6. Summary>>

The eNodeB 100 of the embodiments of the present disclosure have beendescribed above with reference to FIGS. 1-24. According to theseembodiments, allocation of communication resources to a UE 200 iscontrolled based on the setting of the link direction of a channel inwhich the link direction can be dynamically set for each sub-frame, andthe location of the UE 200 in the cell 10.

For example, as in the first embodiment and the second embodiment, thelink direction is dynamically set for each sub-frame of the firstfrequency band, and the link direction is set for each sub-frame of thesecond frequency band so that the difference in link direction betweenthe cell 10 and a cell (an adjacent cell or a macrocell) related to thecell 10 is reduced. And, communication resources of the first frequencyband are not allocated to a UE 200 which is located in the peripheralportion of the cell 10.

By thus setting the TDD configuration and allocating communicationresources, communication resources of a frequency band in which the linkdirection is dynamically set are allocated only to a UE 200 which isallocated in the central portion of the cell 10. Therefore, transmissionpower of the communication resources can be reduced. As a result, anuplink signal on the communication resources does not substantiallyinterfere with a downlink signal of a related cell, and a downlinksignal on the communication resources does not substantially interferewith an uplink signal of a related cell. Specifically, in a frequencyband in which the link direction is dynamically set, interference suchas those shown in FIGS. 4-6 does not substantially occur. Note that onlycommunication resources of a frequency band in which the difference inlink direction from a related cell is small are allocated to a UE 200which is located in the peripheral portion of the cell 10. Of course, inthe frequency band, interference such as those shown in FIGS. 4-6 doesnot substantially occur. Therefore, in a radio communication systememploying TDD, by dynamically setting the link direction, interferencebetween adjacent cells can be reduced while improving throughput.

Also, for example, as in the third embodiment and the fourth embodiment,communication resources in a sub-frame in which the link direction inthe cell 10 is different from the link direction in a cell (an adjacentcell or a macrocell) related to the cell 10 are not allocated to a UE200 which is located in the peripheral portion of the cell 10.

By thus allocating communication resources, communication resources areallocated only to a UE 200 which is allocated in the central portion ofthe cell 10, in a sub-frame of a radio frame in which the link directionis different between the cell 10 and a related cell. Therefore, in thecell 10, transmission power in the sub-frame can be reduced. As aresult, in the sub-frame, an uplink signal of the cell 10 does notsubstantially interfere with a downlink signal of a related cell, and adownlink signal of the cell 10 does not substantially interfere with anuplink signal of a related cell. Specifically, even in a sub-frame inwhich the link direction is different between the cell 10 and a relatedcell, interference such as those shown in FIGS. 4-6 does notsubstantially occur. Also, of course, even in a sub-frame of a radioframe in which the link direction is the same between adjacent cells,interference such as those shown in FIGS. 4-6 does not substantiallyoccur. Therefore, in a radio communication system employing TDD, bydynamically setting the link direction, interference between adjacentcells can be reduced while improving throughput.

The preferred embodiments of the present invention have been describedabove with reference to the accompanying drawings, whilst the presentinvention is not limited to the above examples, of course. A personskilled in the art may find various alterations and modifications withinthe scope of the appended claims, and it should be understood that theywill naturally come under the technical scope of the present invention.

Although, for example, in the above embodiments, the assumed radiocommunication system is compliant with LTE or LTE-Advanced, the presenttechnology is not limited to this example. For example, the assumedradio communication system may be a radio communication system which issimilar to LTE or LTE-Advanced, or may be a radio communication systemwhich is compliant with a standard which is further developed from LTEor LTE-Advanced.

Also, although, in the above embodiments, a communication control devicewhich performs a communication control on a cell is an eNodeB of LTE orLTE-Advanced, the present technology is not limited to this example. Forexample, the communication control device may be a base stationcompliant with other communication standards, or may be a device whichis a part of the base station. Also, the communication control devicemay be another device which controls a base station.

Also, although, in the above embodiments, a terminal device whichcommunicates in a cell is a UE of LTE or LTE-Advanced, the presenttechnology is not limited to this example. For example, the terminaldevice may be a terminal device compliant with another communicationstandard.

Additionally, the present technology may also be configured as below.

-   (1)

A communication control device including:

a radio communication unit which communicates with one or more terminaldevices in a cell over a channel in which a link direction is allowed tobe dynamically set for each sub-frame which is a unit of time in radiocommunication; and

a control unit which controls allocation of communication resources tothe terminal device based on the setting of the link direction of thechannel and a location of the terminal device in the cell.

-   (2)

The communication control device according to (1), wherein

the channel includes at least a first frequency band and a secondfrequency band,

the communication control device further includes a setting unit whichdynamically sets a link direction for each sub-frame of the firstfrequency band, and sets a link direction for each sub-frame of thesecond frequency band so that a difference in link direction between thecell and a cell related to the cell is reduced, and

the control unit does not allocate communication resources of the firstfrequency band to a terminal device which is located in a peripheralportion of the cell.

-   (3)

The communication control device according to (2), wherein

the related cell is a cell which is adjacent to the cell.

-   (4)

The communication control device according to (3), wherein

the cell is a macrocell which covers all or part of a small cell, and

the setting unit causes a communication node in the small cell to set alink direction for each sub-frame in the small cell so that a differencein link direction between the cell and the small cell is reduced.

-   (5)

The communication control device according to (4), wherein

the setting unit, when the small cell is located in a peripheral portionof the cell, causes the communication node of the small cell to set thelink direction of the second frequency band in the small cell so that adifference in link direction between the cell and the small cell isreduced.

-   (6)

The communication control device according to (5), wherein

the communication node, when the small cell is located in a peripheralportion of the cell, dynamically sets a link direction for eachsub-frame of a frequency band which is different from the secondfrequency band, and does not allocate communication resources of thedifferent frequency band to a terminal device which is located in aperipheral portion of the small cell.

-   (7)

The communication control device according to any one of (4) to (6),wherein

the setting unit, when the small cell is not located in a peripheralportion of the cell, causes the communication node in the small cell toset the link direction of the first frequency band in the small cell sothat a difference in link direction between the cell and the small cellis reduced.

-   (8)

The communication control device according to (7), wherein

the communication node, when the small cell is not located in aperipheral portion of the cell, dynamically sets a link direction foreach sub-frame of a frequency band which is different from the firstfrequency band, and does not allocate communication resources of thedifferent frequency band to a terminal device which is located in aperipheral portion of the small cell.

-   (9)

The communication control device according to any one of (4) to (8),wherein

the setting unit notifies the communication node of the link directionfor each sub-frame of the first frequency band or the link direction foreach sub-frame of the second frequency band which have been set by thesetting unit, and causes the communication node to set the linkdirection for each sub-frame in the small cell.

-   (10)

The communication control device according to any one of (4) to (9),wherein

the control unit reduces transmission power in the cell in a sub-framein which a link direction in the cell is different from a link directionin the small cell.

-   (11)

The communication control device according to (2), wherein

the cell is a small cell, and

the related cell is a macrocell which covers all or part of the cell.

-   (12)

The communication control device according to (11), wherein

in the related cell, communication resources of a frequency bandcorresponding to a location of a terminal device are allocated to theterminal device, and

the second frequency band is a frequency band which is allocated to aterminal device which is located in a peripheral portion of the relatedcell when the cell is located in a peripheral portion of the relatedcell, and a frequency band which is allocated to a terminal device whichis not located in a peripheral portion of the related cell when the cellis not located in a peripheral portion of the related cell.

-   (13)

The communication control device according to (11) or (12), wherein

the control unit requests a communication node of the related cell toreduce transmission power in the related cell in a sub-frame in whichthe link direction of the second frequency band in the cell is differentfrom the link direction of the second frequency band in the relatedcell.

-   (14)

The communication control device according to any one of (2) to (13),wherein

the setting unit statically or quasi-statically sets the link directionfor each sub-frame of the second frequency band.

-   (15)

The communication control device according to any one of (2) to (14),wherein

the first frequency band and the second frequency band are each acomponent carrier.

-   (16)

The communication control device according to (1), wherein

the control unit does not allocate communication resources in asub-frame in which a link direction in the cell is different from a linkdirection in a cell related to the cell to a terminal device which islocated in a peripheral portion of the cell.

-   (17)

The communication control device according to (16), wherein

the related cell is a cell which is adjacent to the cell.

-   (18)

The communication control device according to (16), wherein

the cell is a small cell, and

the related cell is a macrocell which covers all or part of the cell.

-   (19)

A communication control method including:

communicating with one or more terminal devices in a cell over a channelin which a link direction is allowed to be dynamically set for eachsub-frame which is a unit of time in radio communication; and

controlling allocation of communication resources to the terminal devicebased on the setting of the link direction of the channel and a locationof the terminal device in the cell.

-   (20)

A terminal device including:

a radio communication unit which communicates with a base station in acell over a channel in which a link direction is allowed to bedynamically set for each sub-frame which is a unit of time in radiocommunication,

wherein the radio communication unit communicates with the base stationaccording to allocation of communication resources to the terminaldevice itself by the base station based on the setting of the linkdirection of the channel and a location of the terminal device itself inthe cell.

REFERENCE SIGNS LIST

-   10 cell-   11, 31, 41 eNodeB-   13, 33, 43 downlink signal-   23, 25, 27 uplink signal-   21 UE-   30 macrocell-   40 small cell-   100 eNodeB-   110 radio communication unit-   120 network communication unit-   130 storage unit-   140, 150, 160, 170 processing unit-   141 terminal location measurement unit-   143 traffic rate measurement unit-   145, 155, 165 link direction setting unit-   147, 167, 177 resource control unit-   149, 159, 169, 179 power control unit-   200 user equipment (UE)-   210 radio communication unit-   220 storage unit-   230 processing unit

The invention claimed is:
 1. A communication control device comprising:circuitry configured to: communicate with one or more terminal devicesin a first cell over a channel in which a link direction can be changedfor individual sub-frames, wherein a sub-frame is a unit of time inradio communication; and control transmission power of individualsub-frames, wherein the channel includes at least a first frequency bandand a second frequency band, and the circuitry is configured to requesta communication node of a second cell to reduce the transmission powerfor the sub-frame in which a second link direction of the second cell isdifferent from the link direction of the first cell.
 2. Thecommunication control device of claim 1, wherein the link direction forthe individual sub-frames can be changed to a downlink direction, andthe circuitry is configured to communicate with the one or more terminaldevices using one or more second sub-frames having a link directionfixed in the downlink direction.
 3. The communication control device ofclaim 1, wherein the circuitry is configured to control the transmissionpower to reduce interference of downlink and uplink signals in differentcells.
 4. The communication control device of claim 1, wherein thecircuitry is configured to control the transmission power to bedifferent in sub-frames of different types.
 5. The communication controldevice of claim 1, wherein the circuitry is configured to change thelink direction based on the second link direction of a sub-frame in thesecond cell.
 6. The communication control device of claim 1, wherein thecircuitry is configured to communicate with the one or more terminaldevices using time-division duplexing in which the sub-frame is a unitof time in the time-division duplexing.
 7. The communication controldevice of claim 1, wherein the circuitry is configured to set the secondlink direction to reduce a difference between link directions ofsub-frames of the first cell and a second cell.
 8. A terminal devicecomprising: circuitry configured to: communicate with a communicationcontrol device in a first cell over a channel in which a link directioncan be changed for individual sub-frames, wherein a sub-frame is a unitof time in radio communication, and the channel includes at least afirst frequency band and a second frequency band, wherein a second linkdirection for the individual sub-frames of the second frequency band isset to reduce a difference between link directions of sub-frames of thefirst cell and a second cell, and wherein transmission power ofindividual sub-frames is controllable.
 9. The terminal device of claim8, wherein the link direction for the individual sub-frames can bechanged to a downlink direction.
 10. The terminal device of claim 8,wherein one or more second sub-frames have a link direction fixed in adownlink direction.
 11. The terminal device of claim 8, wherein thetransmission power is controlled to reduce interference of downlink anduplink signals in different cells.
 12. The terminal device of claim 8,wherein the transmission power is different in sub-frames of differenttypes.
 13. The terminal device of claim 8, wherein the link direction ischanged based on the second link direction of a sub-frame in the secondcell.
 14. The terminal device of claim 13, wherein second cell neighborsor overlaps with the first cell.
 15. The terminal device of claim 8,wherein the circuitry is configured to communicate with thecommunication control device using time-division duplexing in which thesub-frame is a unit of time in the time-division duplexing.
 16. Theterminal device of claim 8, wherein the link direction for individualsub-frames of the first frequency band is at least partially differentfrom the second link direction for individual sub-frames of the secondfrequency band.
 17. The terminal device of claim 16, wherein the firstfrequency band and the second frequency band are aggregated to be usedfor carrier aggregation.
 18. A communication control device comprising:circuitry configured to: communicate with one or more terminal devicesin a first cell over a channel in which a link direction can be changedfor individual sub-frames, wherein a sub-frame is a unit of time inradio communication, and the channel includes at least a first frequencyband and a second frequency band; control transmission power ofindividual sub-frames; and reduce the transmission power for thesub-frame in which the link direction in the first cell is differentfrom a second link direction in a second cell.
 19. The communicationcontrol device of claim 18, wherein the circuitry is configured toreduce the transmission power for the sub-frame in which the linkdirection of the second frequency band in the first cell is differentfrom the second link direction of the second frequency band in thesecond cell.
 20. The communication control device of claim 18, whereinthe circuitry is configured to reduce the transmission power for thesub-frame in which the link direction of the first frequency band in thefirst cell is different from the second link direction of the firstfrequency band in the second cell.